Excel on Mac tries to open every file

Question

Opening Excel 365 on my Mac OS 12.7.6 it tries to open every file on my system. I've cleared the startup folder and rebooted but it's still happening. I can't get to the Excel preferences because the system is busy trying to open every file extension

How do i fix this please.

Answer 1

This usually is the result of a Preference setting as you may have realized. This procedure will get you into the Preferences on launch but requires accurate timing... You may have to try more than once:

Excel Opens All

1. While Excel is not running, launch the program & immediately press Command+Comma to launch the Preferences dialog... this is where timing is the key.
   1. if Preferences doesn't open use Option+Command + esc to Force Quit the program
   2. Be sure to clear the checkbox to Restart the program
2. If the Preferences dialog successfully opens go to the General pane then clear the field for At startup open all files in:
3. Restart Excel

Please don't embark on the extensive litany of speculative misdirection spewed forth by the AI bot.

Answer 2

Excel is likely failing at startup because its preferences or Office settings are corrupted. Because Excel is too busy to reach Preferences, remove the preference files and Office settings from Finder so Excel starts clean.

Follow these steps in order:

1. Quit Excel and all Office apps

• On the Apple menu, select Force Quit.
• Select Microsoft Excel (and any other Office apps) and choose Force Quit.
• Repeat until all Office apps are closed.

2. Remove Excel’s main preference file
3. In Finder, on the Go menu, select Home.
4. Open the Library folder. (If Library is hidden, hold down the OPTION key while selecting the Go menu, then choose Library.)
5. Open Preferences.
6. Find com.microsoft.Excel.plist and drag it to the Desktop.
7. Start Excel and see if it opens normally without trying to open every file.
   • If the problem is fixed, drag com.microsoft.Excel.plist from the Desktop to the Trash.
   • If the problem persists, quit Excel and move com.microsoft.Excel.plist back to Preferences, then continue.
8. Remove Excel’s secondary preference file
9. Quit all Office for Mac apps again.
10. In Finder, Go > Home > Library > Preferences.
11. Open the Microsoft folder.
12. Drag com.microsoft.Excel.prefs.plist to the Desktop.
13. Start Excel and test again.
    • If fixed, drag com.microsoft.Excel.prefs.plist from the Desktop to the Trash.
    • If not fixed, quit Excel and move it back, then continue.
14. Reset shared Office settings (Office 2016/365 on macOS 12)
15. Make sure all Office apps are closed.
16. In Finder, on the Go menu, hold OPTION and select Library.
17. Open Group Containers.
18. Look for the folder whose name ends with .Office (for example, UBF8T346G9.Office) and open it.
19. Locate com.microsoft.officeprefs.plist and drag it to the Trash.
20. Start Excel and check whether it now opens normally.
    • If the issue persists, quit all Office apps again, go back to Group Containers, and drag the entire .Office folder you found in step 4 to the Trash. This resets Office to first‑run state and recreates the folder on next launch.
21. If the problem still occurs

• Perform a clean startup (Safe Boot) of macOS to rule out interference from background software, then start Excel and test. For details, see the clean startup article referenced below.
• If Excel still misbehaves even after preferences and Office settings are reset, uninstall and reinstall Office for Mac, then sign in and activate again.

These steps remove corrupted Excel and Office settings that can cause abnormal startup behavior, including attempting to open inappropriate files at launch.

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References:

• Excel for Mac error: "The application Microsoft Excel quit unexpectedly"
• "Microsoft Excel has encountered a problem and needs to close" when starting Excel for Mac
• How to use a "clean startup" to determine whether background programs are interfering with Office for Mac
• Microsoft Office apps for Mac quit unexpectedly - Microsoft Q&A